Effect of paravertebral dexmedetomidine administration on intraoperative anaesthetic drug requirement and incidence of post thoracotomy pain syndrome

Abstract

Introduction. Administration of dexmedetomidine as an adjuvant to local anaesthetic via epidural and paravertebral route has shown to decrease surgical stress response, improve quality and duration of postoperative analgesia and decrease opioid requirements. 1 Good perioperative analgesia has shown to decrease the incidence of post thoracotomy pain syndrome. The aim of the present study was to assess the effect of paravertebral dexmedetomidine on intraoperative anaesthetic drug requirement, post‐operative pain control and rescue analgesic requirements and the incidence of post thoracotomy pain syndrome. Methods. In this prospective randomized double blind trial, 30 adult patients undergoing thoracotomy were randomized to receive paravertebral block with either 15ml of 0.75% ropivacaine bolus followed by infusion of 0.2% ropivacaine at 0.1ml/kg/hr (Gr‐R) or 15ml of 0.75% ropivacaine plus dexmedetomidine 1mcg/kg bolus followed by infusion of 0.2% ropivacaine plus 0.2mcg/kg/hr of dexmedetomidine at 0.1ml/kg/hr (Gr‐D). Intraoperative anaesthetic requirement, postoperative pain scores and requirement of rescue does of morphine were recorded for 24 hours after surgery. The incidence of post thoracotomy pain syndrome was noted at 2 months after surgery. Results. The demographic characteristics of the patients, duration of anaesthesia and surgery were comparable between two groups. The amount of propofol required for induction of anaesthesia (Gr‐D 49.33+/‐20.51mg v 74.33+/‐18.40mg in Gr‐R, p=0.002), total amount of fentanyl required during surgery (Gr‐D 115.33+/‐33.77 mcg v 178.67+/‐32.48 mcg in Gr‐R, p<0.001) and the end tidal concentration of isoflurane required to maintain state entropy (o 60 ) during surgery was significantly less in Gr‐ D. Post‐operative VAS scores at 1 hr (p=0.02), 2 hr (p=0.006), 4 hr (p=0.02), and 8 hrs (p=0.04] after the surgery, number of rescue analgesics (Gr‐D 1(0‐3) v 3(1‐5) in Gr‐R; p<0.001) and total dose of morphine required (Gr‐D 3.60+/‐2.58 mg v 9.60+/‐3.04 mg in Gr‐R; p<0.001) during post‐operative period were significantly less in Gr‐D. The incidence of post thoracotomy pain syndrome was comparable (Gr‐D 57.14% v 55.55% in Gr‐R, p=0.502) between two groups. Discussion. Paravertebral dexmedetomidine decreases intraoperative anaesthetic drug requirement, provide better pain relief and reduces rescue opioid requirement in the postoperative period. However it does not affect the incidence of post thoracotomy pain syndrome.